In order to improve operability, computer graphics utilizes separate colors for entries and background in an input screen as disclosed in Japanese Patent Publication Hei 7-325666. Instead of using a mouse or a keyboard, an input pen or stylus is used to input information, and the input pen is also used with a computer in video conferencing. For example, a liquid chrystal display device as disclosed in Japanese Patent Publication Hei 9-114591 recognizes coordinates of an input pen position when the input pen is placed on the liquid chrystal display unit. Based upon these coordinates, as the input pen moves on the liquid chrystal display unit, a trace is displayed in a predetermined color. In the above display unit, the traces or lines are displayed over existing images by superimposing the lines. By using a large color display screen, the above display is highly useful for conferences, presentations or education.
In the above described input pen system, the color of an input pen is predetermined prior to use. In certain instances, the selected pen color may be identical to or substantially similar to a background color of the display image. As a result of the above undesirable input color selection, the line traces of the input pen may not be easily discernible. In particular, when a large display unit is used for a presentation to a group of people and input pen traces are not easily identifiable from the existing image or background color, the display presentation system has a serious flaw. In other words, the need for specifying an input color substantially reduces the operability and convenience.
For presentations using a large color display unit, when a group of people recognizes superimposed line traces in images, it is highly desirable for the line traces and other graphics to be easily recognized. Even when a small screen device or an individual document generating device such as a PC is used to prepare the presentation material, the lines and images are easily discernible. However, the same data may not be easily discernible on a large screen without a sufficient amount of projection light. In these document generation devices such as PC's, a user specifies the color of lines and characters to indicate emphasis, and an appropriate color with respect to the background color is not automatically selected.
In a different application of the line trace, a karaoke machine generally indicates words in a predetermined color that is easy to read against the background. However, the color of words may sometimes becomes substantially similar to that of the still or animated background, and it becomes difficult to read the words.
In general, a complementary color is used to distinguish a display color or a pen color from a background color. The complementary color is a color that generates gray when it is mixed with the background color. However, a simple complementary color is not necessarily the most readily visible to all people. In fact, a certain color combination is not always pleasing to many, and may be unsuitable in some business situations. For example, the background color and the pen color are respectively green and pink for the complementary color combination. The color pink may not be appropriate for presentation material.
The above described problems demand a method and a device for automatically selecting a desirable input pen color with respect to a background color to maximize the visibility of input images.